The invention relates to a capped electric lamp comprising:
a lamp vessel closed in a vacuumtight manner, in which an electric element is positioned; PA1 a lamp cap connected to the lamp vessel, which lamp cap comprises electric contacts and a metal shell having ends and inwardly directed projections; PA1 an insulator body having a circumferential outer surface between a first and a second end face, enclosed in the metal shell, in which outer surface recesses are distributed over a cross-section, inwardly directed projections of the metal shell entering the said recesses; PA1 current supply conductors to the electric element issuing from the lamp vessel to the exterior and connected to electrical contacts of the lamp cap. PA1 the outer surface of the insulator body has flattened portions between the recesses; PA1 inwardly directed projections of the metal shell press into the recesses with clamping fit.
Such a capped electric lamp, which may be used as a headlamp in a motor vehicle, is known from DE-GM-8 907 108.5, corresponding to U.S. Pat. No. 5,010,272.
The known lamp has an insulator body with recesses on a cross-section at the second end face, tags being pressed inwards to engage into said recesses, while on a cross-section at a distance therefrom it has a circumferential rim with which other tags cooperate.
A disadvantage of this lamp is that the insulator body is not immovably enclosed in the metal shell. In fact, the tags at the second end face cannot be pressed inwards until after the insulator body has been inserted into the metal shell. These tags can then not be pressed further than up to the point where they touch the insulator body. Since deformations in the metal shell occurring while projections thereof are pressed inwards not only have a plastic but also an elastic component, the inwardly pressed tags will spring back a little. The result of this is that play arises between the insulator body and the shell. This play may have axial, radial and tangential components.
This entails the risk that, owing to vibrations of a vehicle to which the lamp is fastened, or as a result of a manipulation with the lamp, for example, the insertion of the lamp in a lampholder, mechanical forces are exerted on the current supply conductors, so that an electric connection is broken.